settings: Set an intelligent default for ALLOWED_HOSTS.

docs/prod-install.md

@@ -89,9 +89,6 @@ These settings include:
   your configuration using `manage.py send_test_email` to confirm
   your outgoing email configuration is working correctly.
 
-- `ALLOWED_HOSTS`: Replace `*` with the fully qualified DNS name for
-  your Zulip server here.
-
 ## Step 4: Initialize Zulip database
 
 At this point, you are done doing things as root.  To initialize the

zproject/prod_settings_template.py

@@ -111,7 +111,7 @@ NOREPLY_EMAIL_ADDRESS = "noreply@example.com"
 # header. See Django's documentation here:
 # <https://docs.djangoproject.com/en/1.9/ref/settings/#allowed-hosts>.
 # Zulip adds 'localhost' to the list automatically.
-ALLOWED_HOSTS = ['zulip.example.com']
+ALLOWED_HOSTS = [EXTERNAL_HOST]
 
 ### OPTIONAL SETTINGS
 

zproject/settings.py

@@ -212,7 +212,6 @@ REQUIRED_SETTINGS = [("EXTERNAL_HOST", "zulip.example.com"),
                      ("AUTHENTICATION_BACKENDS", ()),
                      ("NOREPLY_EMAIL_ADDRESS", "noreply@example.com"),
                      ("DEFAULT_FROM_EMAIL", "Zulip <zulip@example.com>"),
-                     ("ALLOWED_HOSTS", ['zulip.example.com', '127.0.0.1', 'localhost']),
                      ]
 
 if ADMINS == "":